In recent years, measurement of organic carbon concentration in municipal water and wastewater, water for various sorts of plants, river water and the like, has become an important item of pollution surveys and the like. Total organic carbon meters (TOC meters) are used for such measurement of organic carbon concentration.
Moreover, the demand for TOC measurement has expanded to solid samples. In TOC meters for measurement of solid samples, a set quantity of solid sample is placed onto a ceramic sample tray and each sample tray is inserted into a quartz glass combustion tube, whereby the organic matter in the solid sample is combusted (subjected to an oxidation reaction), and the generated carbon dioxide is measured with an infrared detector.
In this sort of TOC meter, combustion tube 1 is arranged horizontally inside a tubular combustion reaction furnace (combustion furnace) 2 heated to about 900° C. so that the sample tray 6 inserted into the combustion tube 1 will be heated (see FIG. 5 and FIG. 6). Furthermore, a carrier gas inlet 11 is formed at one end part (the right part) of the combustion tube 1 so that carrier gas (for example, oxygen gas of 99.99 weight percent purity) will flow through the inside of the combustion tube 1 in a fixed direction (for example, from right to left). Furthermore, the other end part (left part) of the combustion tube 1 is filled with an oxidation catalyst 5, the carbon content, etc. generated from the solid sample reaches the oxidation catalyst layer 5 together with the carrier gas, and is oxidized by the oxidation catalyst, turning into carbon dioxide.
To the other end part (left part) of the combustion tube 1, a non-dispersive infrared sensor (NDIR) is connected across a drain separator, and the carbon dioxide gas and carrier gas from the combustion tube 1 are guided to the NDIR, and the carbon content in the solid sample is detected (for example, see Patent Literature 1).
Using this sort of TOC meter, in order for the operator to replace a sample tray 6 on which one solid sample has been placed with a sample tray 6 on which the next solid sample has been placed, the temperature of the replacement work area has to be kept low, so one end part (the right part) of the combustion tube 1 is formed so as to protrude a certain distance outside the electric furnace 2, and a sample introduction port section (sample introduction mechanism) is connected to that one end part (right part) of the combustion tube 1. Furthermore, the operator pushes the sample tray 6 arranged inside one end part of the combustion tube 1 with a sample introduction rod 17 through the sample introduction port section, thereby moving it in a set direction (for example, from right to left) and arranging it inside the central part of the combustion tube 1.
Here, FIG. 5 is a simplified diagram of one example of the sample introduction port section of a conventional TOC meter.
Sample introduction port section 20 comprises a round tubular case 13 with a sample introduction opening 13c formed in the top wall, a round (for example, 6 mm diameter) rod opening 13d formed in the right wall and a gas introduction opening 13e formed in the bottom wall, a cover 14 arranged on the sample introduction opening 13c, a sample introduction rod 17 inserted across an O-ring 13a in a set direction through the rod opening 13d, and a carrier gas inlet 11 connected to gas inlet opening 13e. 
Sample introduction rod 17 is made of stainless steel and has a 6 mm diameter cylindrical shape, made so that a sample tray 6 can be arranged on its front end part and having a manipulation handle formed on its rear end part.
Cover 14 is designed to move several mm up and down through turning of a screw, and is designed to ensure air-tightness of the inside of the case 13 by tightly fitting to the periphery of the sample introduction opening 13c in the top wall when positioned in its lower position and to allow opening of the inside of the case 13 by sliding horizontally when in its upper position.
Furthermore, when analyzing a solid sample arranged inside the central part of the combustion tube 1, carrier gas is introduced at 500 ml/min into the case 13 through the carrier gas inlet 11, and the carrier gas flows through the inside of the combustion tube 1 in a set direction (for example, from right to left) at 500 ml/min.
With this sort of sample introduction port section 20, the operator positions the cover 14 at the upper position by turning the handle at the top end of the screw with his hand, slides the cover 14 with his hand horizontally, and then arranges a sample tray 6 at the front end part of the sample introduction rod 17 located inside the case 13 through the sample introduction opening 13c. The operator then slides the cover 14 horizontally with his hand and turns the handle at the top end of the screw with his hand, thereby positioning the cover 14 at the lower position. Next, the operator moves the sample introduction rod 17 by pushing it in the set direction, thereby arranging the sample tray 6 in the central part of the inside of the combustion tube 1.
Furthermore, FIG. 6 is a simplified diagram of another example of the sample introduction port section of a conventional TOC meter. Parts which are the same as in the sample introduction port section 20 described above will be assigned the same reference symbols.
Sample introduction port section 30 comprises a round tubular (for example, 30 mm diameter) sample introduction and rod opening 23d in the right wall, a round tubular case 23 with a gas introduction opening 23e formed in its bottom wall, a sample introduction rod 17 which is inserted in a set direction through the sample introduction and rod opening 23d, and a carrier gas inlet 11 connected to the gas introduction opening 23e. 
A fixed flow rate pump 31 which suctions 500 ml/min is connected to the other end part (left part) of the combustion tube 1.
To analyze a solid sample arranged inside the central part of the combustion tube 1, carrier gas is introduced at 1,000 ml/min into the case 23 through carrier gas inlet 11, carrier gas is made to flow through the inside of the combustion tube 1 in a set direction (for example, from right to left) by the fixed flow rate pump 31 at 500 ml/min, and the quantity of carrier gas exceeding the flow rate suctioned by fixed flow rate pump 31 is discharged through the gap between the sample introduction and rod opening 23d and sample introduction rod 17. This prevents air from entering inside the combustion tube 1.
With this sort of sample introduction port section 30, the operator arranges a sample tray 6 at the front end part of the sample introduction rod 17, and then inserts the sample introduction rod 17 with his hand inside the case 23 through the sample introduction and rod opening 23d. Next, the operator moves the sample introduction rod 17 by pushing it with his hand in the set direction, thereby arranging the sample tray 6 in the central part inside the combustion tube 1.